Firtel R A, Kindle K, Huxley M P
Fed Proc. 1976 Jan;35(1):13-22.
The organization of the genome and the synthesis and processing of heterogeneous nuclear RNA (HNRNA) in the cellular slime mold Dictysotelium discoideum have been analyzed. Approximately 60-70% of the genome of Dictyostelium consists of interspersed reiterated and single-copy sequences. The interspersed reiterated sequences have an average length of 250-400 nucleotides. Approximately 50% of the reiterated DNA sequences consist of long noninterspersed sequences. The results of analyses of ynRNA synthesis and processing have been incorporated into a model. According to the model the primary genetic transcript of Dictyostelium is synthesized as a molecule that is 25% larger than mRNA. The bulk of the hnRNA is synthesized from a unit consisting of a short reiterated DNA sequence transcript at the 5' end of the molecule and a single-copy sequence of approximately 1,200 nucleotides in length. In the processing of the mRNA precursor, there appears to be a loss of the majority of the repetitive sequence at the 5' end. The genome contains interspersed sequences of poly (dT)25. These sequences, which appear to be at the 3' terminus of the transcription unit, are transcribed directly into the heterogenous nuclear RNA and are contained within the messenger RNA. During the processing of the heterogeneous nuclear RNA, a poly (A) sequence of approximately 125 nucleotides in length is added posttranscriptionally to the 3' end of the molecule.
对细胞黏菌盘基网柄菌的基因组组织以及不均一核RNA（hnRNA）的合成与加工进行了分析。盘基网柄菌基因组约60 - 70%由散布的重复序列和单拷贝序列组成。散布的重复序列平均长度为250 - 400个核苷酸。约50%的重复DNA序列由长的非散布序列组成。对hnRNA合成与加工的分析结果已纳入一个模型。根据该模型，盘基网柄菌的初级基因转录本合成为一个比mRNA大25%的分子。大部分hnRNA由一个单元合成，该单元在分子5'端由一个短的重复DNA序列转录本和一个长度约为1200个核苷酸的单拷贝序列组成。在mRNA前体的加工过程中，5'端的大部分重复序列似乎会丢失。基因组包含聚（dT）25的散布序列。这些序列似乎位于转录单元的3'末端，直接转录到不均一核RNA中并包含在信使RNA内。在不均一核RNA的加工过程中，转录后在分子3'端添加一个长度约为125个核苷酸的聚（A）序列。
